Compatibilized polymer blends formed using a multifunctional agent

ABSTRACT

A process for forming a compatibilized blend of general purpose rubbers (GPR) and a halogenated poly(isobutylene-co-4-methylstyrene) through solventless reactions utilizing a multifunctional agent containing a diene reactive group and a benzylic halo reactive group.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Continuation Application of U.S. Ser. No.08/977,711, filed on Nov. 25, 1997, now, U.S. Pat. No. 6,294,613, whichclaims priority to U.S. Ser. No. 60/034,290 filed on Dec. 18, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to compatibilized polymer blends formed usinga multifunctional agent in a polymer blend, preferably consisting ofgeneral purpose rubbers and benzyl halide containing polymers.

2. Related Art

Relatively saturated elastomeric polymers, such as butyl rubber, whichis a copolymer of isobutylene with a small percentage of isoprene unitsare known. These polymers demonstrate low air permeability, relativelylow glass transition temperatures, broad damping peaks, excellentenvironmental aging resistance, and other such properties which renderthese polymers of commercial significance in blends with polymers or intire production. Butyl rubber generally is incompatible with most otherpolymers.

It has been known for some time that blends of incompatible polymers canbe improved in some cases by adding a suitable compatibilizer so as toalter the morphology of these blends. More particularly, to besuccessful it has been necessary to reduce the domain sizes for both ofthe polymers in the blend.

It is known in some instances to use block copolymers ascompatibilizers. For example, several studies have shown attempts tocompatibilize rubber-rubber blends of polyisoprene and polybutadiene byusing diblock materials composed of these two materials. See R. Cohen etal. Macromolecules 15, 370, 1982; Macromolecules 12, 131, 1979; J.Polym. Sci., Polym. Phys. 18, 2148, 1980; J. Macromol. Sci.-Phys. B17(4), 625, 1980. Most of these block copolymers have been previouslyproduced by sequential anionic polymerization processes, which are thuslimited to a relatively small number of monomers. It is also known tocompatibilize other blends, such as rubber-plastic blends ofethylene-propylene rubber with polypropylene, by using graft copolymersof these two materials. See A. Y. Coran et al., U.S. Pat. No. 4,299,931,as well as co-pending commonly assigned applications Ser. No. 07/264,484now U.S. Pat. No. 4,999,403 and Ser No. 07/264,485, filed on Oct. 28,1988.

Others have proposed different solutions for preparing compatibilizedblends comprising isoolefin polymers. For example, Wang, in WO 95/09197describes intervulcanizable blends comprising a mixture of a diolefinpolymer or copolymer and a saturated or highly saturated elastomericcopolymer having a number average molecular weight of at least 10,000and containing from about 0.01 up to about 10 mole % of “Y” functionalgroups randomly distributed along and pendant to the elastomeric polymerchain, said Y functional groups containing an olefinic or vinyl doublebond positioned alpha, beta to a substituent group which activates saiddouble bond towards free radical addition reactions. The preferredactivating substituent groups are carboxyl-containing groups,phosphoryl-containing groups, sulfonyl-containing groups,nitrile-containing groups, aromatic ring-containing groups or acombination of such groups.

It would be desirable to obtain a process not employing a solvent. Thepresent invention provides compatibilized blends formed by a solventlessreaction between two generally incompatible polymers with amultifunctional compound/agent.

SUMMARY OF THE INVENTION

The invention is directed to a solventless process for formingcompatibilized blends of general purpose rubbers and benzyl halidepolymers comprising mixing at least one general purpose rubber and abenzyl halide containing polymer in the presence of a multifunctionalagent, said agent comprising a compound represented by the generalformula (X)_(n)—(R)_(m)—(Y)_(p), wherein m is equal to or greater thanzero, and desirably range from about 1 to about 10, n and p are greaterthan zero and desirably range from about 1 to about 100. X is dienereactive group. Preferably the diene reactive group is selected from thegroup consisting of (1) enophiles, (2) free radicals and radical traps,(3) free radical traps, and (4) nucleophiles. R is selected from thegroup consisting of alkyls, aryls, alkyl substituted aryls preferablyhaving from about 1 to about 100 carbon atoms and polymers. And Y is abenzylic halogen reactive group, like a nucleophile. In addition, thepresent invention is also directed to using compatibilized blends of thepresent invention to compatibilize other polymer blends by mixing thecompatibilized blend with at least one general purpose rubber and atleast one polymer to form a new compatibilized blend.

The invention is further directed to a compatibilized blend of generalpurpose rubbers and benzyl halide containing polymers comprising mixinggeneral purpose rubbers, benzyl halide containing polymers and amultifunctional agent comprising a compound having the formula(X)_(n)—(R)_(m)—(Y)_(p), wherein m is equal to or greater than zero, nand p are greater than zero, X is a diene reactive group, R is selectedfrom the group consisting of alkyls, aryls, alkyl substituted arylshaving from about 1 to about 100 desirably 1-20 carbon atoms andpolymers, and Y is a benzylic halide reactive group. In addition, thepresent invention is directed to the cured compatibilized blendsdescribed above.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to compatibilized blends of generalpurpose rubbers (“GPR”) and benzyl halide containing polymers. Thepresent invention is also directed to a process for the production ofcompatibilized blends of GPR and benzyl halide containing polymers.Moreover, the present invention is directed to compatibilized blends ofGPR and poly(isobutylene-co-methylstyrene) containing 4-halomethyleneunits (hereinafter BIPMS) disclosed in U.S. Pat. No. 5,162,445, hereinincorporated by reference. The present invention is further directed toa solventless process for the production of compatibilized blends of GPRand BIPMS. In addition, the present invention is directed to utilizingcompatibilized blends of the present invention to compatibilize otherpolymer blends.

In a particularly preferred embodiment, the compatibilized blends of thepresent invention are comprised of a blend of general purpose rubbersand BIPMS. The benzyl halide copolymers are desirably elastomericcopolymers of isobutylene, a para-methyl styrene containing from about0.5 to about 20 mole percent para-methyl styrene wherein up to about 60mole % of the methyl substituent groups present on the aromatic ringcontain a bromine or chlorine atom. These copolymers and their method ofpreparation are disclosed in U.S. Pat. No. 5,162,445, herebyincorporated by reference. The blends of the present invention mayinclude but are not limited to the following general purpose rubbers:natural rubber (NR), polyisoprene (IR), polybutadiene (BR),poly(styrene-co-butadiene) (SBR), and poly(acrylonitrile-co-butadiene)(NBR).

Generally, the blends of the present invention may comprise from about 5to about 95 percent by weight GPR and from about 5 to about 95 percentby weight benzyl halide containing polymer. Preferably the blendscomprise from about 15 to about 85 percent by weight GPR and from about15 to about 85 percent by weight benzyl halide containing polymer. Mostpreferably, the blends of the present invention are comprised of about30 to about 70 percent by weight GPR and from about 30 to about 70percent by weight benzyl halide containing polymer. The multifunctionalagent employed in the practice of the present invention generallycomprises from about 0.01 to about 10 percent by weight, preferably 0.01to about 3 percent, of the total blend weight.

The process of the present invention may be carried out in a single stepor in two steps. For example, the multifunctional agent may be mixedwith the GPR or the benzyl halide polymer first and then added to theother component with mixing and heating. Alternatively, the process ofthe present invention may be carried out in a single pass or stepwherein the multifunctional agent, GPR, and benzyl halide polymer aremixed and heated together simultaneously.

Utilizing either process described above, the reaction is conductedunder solventless conditions using internal mixers, extruders, andrubber milling equipment. Typical mixers include Brabender™ and Banbury™mixers. As stated above, the rubber compositions are placed in themixers along with the multifunctional agent and reacted under shear andheat to yield the compatibilized blends of the present invention.

The multifunctional agent of the present invention is a multifunctionalcompound containing both a diene reactive group and a benzyl halidereactive group. The multifunctional agent of the present invention hasthe following formula: (X)_(n)—(R)_(m)—(Y)_(p), wherein m is equal to orgreater than zero, and n and p are equal to or greater than one. X is adiene reactive group and may be selected from the group consisting of(1) enophiles, (2) free radicals and free radical traps, (3) freeradical traps and (4) nucleophiles. The enophiles which are useful inthe practice of the present invention include, but are not limited to,maleic anhydride and its activated derivatives, including but notlimited to carboxy maleic, sulfo maleic, methyl maleic, and phenylmaleic, etc., as well as the analogous nitrogen species,triazolinediones. The free radical sources useful in the practice of thepresent invention include, but are not limited to, peroxides, azocompounds, and polymer bond cleavage, i.e., radicals formed during GPRmastication. Preferred peroxides include dicumyl peroxide, di-t-butylperoxide, benzoyl peroxide, bis p-chlorobenzoyl peroxide, and t-butylcumyl peroxide. Preferred azo compounds include 2,2′-azobis(isobutyronitrile); 1,1′-azo bis(cyclohexanecarlonitrile); 4,4′-azobis(4-cyanovaleric acid); and 2,2′-azo bis(2-amidinopropane).

The radicals can either add to the olefin or extract a proton leading topolymeric radicals. These radicals can be trapped using suitable radicalsinks or traps, e.g., sulphides, sulphenylchlorides, and thioacids.Alternately, the radicals can be trapped utilizing free-radicalpolymerizable monomers, e.g., acrylic, and methacrylic acid.

Y is the benzylic halide reactive group and is a nucleophile.Preferably, the nucleophilic groups which are useful in the practice ofthe present invention include, but are not limited to carboxylates,amines, phosphines, alkoxides, phenoxides, and thiolates.

R may be an alkyl, aryl or an alkyl-substituted aryl containing fromabout 1 to about 100 carbon atoms, or a polymer having a Mw up to about100,000. Polymers which are suitable as R may be prepared by controlledpolymerization methods such as “living” anionic, cationic, orfree-radical reactions. These “living polymers” are convenientlyprepared by contacting the monomers or combination of monomers with apolymerization initiator in the presence of an inert organic diluentwhich does not participate in or interfere with the polymerizationreaction. For example, dimethylaminopropyllithium may be used toinitiate the “living” polymerization of dienes like butadiene andisoprene. This “living” chain is then terminated with propylene sulfide.The polymer thus has an end which can react with benzylhalide and asecond end which is diene reactive. Alternatively, polymers suitable asR may be obtained by ring-opening polymerization of cyclic monomersusing a suitable functionalized initiator. The molecular weight of the Rpolymer may vary depending upon the application; however, typicallypolymers desirably having a molecular weight ranging from about 500 toabout 100,000 are useful in the practice of the present invention.

The compatibilized blends of the present invention may be curedgenerally using curing systems known in the rubber industry. Forexample, curing systems useful in curing the blends of the presentinvention include but are not limited to systems comprising sulfurcompounds, zinc compounds, metal compounds, radical initiators, etc.Specific compounds useful as curatives in the present invention include,but are not limited to, zinc oxide, stearic acid, tetramethylthiuramdisulfide (TMTD), 4,4′-dithiodimorpholine (DTDM), tetrabutylthiunramdisulfide (TBTD), benzothiazyl disulfide (MBTS),hexamethylene-1,6,-bisthiosulfate disodium salt dihydrate (ERP 390),2-(morpholinothio) benzothiazole (MBS or MOR), blends comprising 90% byweight MOR and 10% by weight MBTS (MOR90), N-oxydiethylenethiocarbamyl-N-oxydiethylene sulfenamide (OTOS) zinc 2-ethyl hexanoate(2EH); and MC sulfur.

The present invention, while not meant to be limited by, may be betterunderstood by reference to the following examples.

In the following examples, the benzyl halide containing polymer (BIPMS)was brominated poly(isobutylene-co-4-methyl styrene containing 7.5 wtpercent, 4-methyl styrene, and 2 wt percent benzyl bromide, and having aMooney viscosity ML(1+8) 125° C. of 45±5.

EXAMPLE I

Compatibilization of Natural Rubber with BIPMS:

Radicals Generated During Mastication and TetramethylammoniumMercaptoacetate Salt as Radical Trap.

a. The tetramethylammonium mercaptoacetate salt (hereinafter “salt”) wasprepared through neutralization of commercially available materials.0.921 g of 0.01 M Mercaptoacetic acid (obtained from Aldrich) wasneutralized with 3.646 g of 0.01 M tetramethylammonium hydroxide(obtained as a 25 weight percent methanol solution from Aldrich). Thewater and methanol were removed under vacuum to yield a white salt.

b. Two Pass Compatibilized Blend: 40 g of NR was placed in a Brabender™cavity along with 0.25 g of the salt, prepared previously. The rubbersalt mixture was masticated at 50 rpm and 60° C. for 15 minutes. Thecontents of the Brabender™ were removed. A fraction of the reactednatural rubber was placed in the Brabender™ along with 35 g of BIPMS.The mixture was mixed at 20° C. and 10 rpm for 5 minutes. The Brabender™was then heated to 50° C. at which time the speed was increased to 100rpm. Under these conditions, the temperature increased to 115° C. Themixture was kept at 100 rpm and 115° C. for 15 minutes and then removed.The compatibilized blend was then compared to a noncompatibilized blendusing electron microscopy. The results are reported in Table 1 below.

EXAMPLE 2

Graft Reaction of Natural Rubber with BIPMS

Using Radicals Generated from Peroxide (Dicumyl Peroxide) andTetrabutylammonium Methacrylate as Radical Trap in a Single Pass Mix

a. The salt was prepared by neutralizing commercially availablematerials.

0.874 g of methacrylic acid was neutralized with 10 ml of a 1 molarsolution of tetrabutylammonium hydroxide in methanol. The methanol wasremoved under nitrogen to yield a white salt.

b. One pass compatibilized blend: 33.2 g BIPMS and 14.23 g of naturalrubber were placed in a Brabender™ mixer. The rubber was mixed 5 minutesat 85-90° C. and 60 rpm. The temperature was raised to 150° C. and 0.051g of dicumyl peroxide and 0.471 g of the tetrabutylammonium methacrylatewas added. The mix was reacted for an additional five minutes. Thecompatibilized blend was then compared to a noncompatibilized blendusing electron microscopy. The results are reported in Table 1 below.

EXAMPLE 3

Graft Reaction of Polybutadiene with BIPMS

Using Radicals Generated from Peroxide (Dicumyl Peroxide) andTetrabutylammonium 6,8 Dithiooctanoate as Radical Trap in a Two Pass Mix

a. The salt was prepared by neutralizing commercially availablematerials. 0.2064 g of 6,8-dithiooctanoic acid was neutralized with 10.1ml of a 1 molar solution of tetrabutylammonium hydroxide in methanol.The methanol and water were removed under nitrogen to yield a yellowproduct.

b. Two pass compatibilized blend: 47.12 g of polybutadiene was placed ina Brabender™ mixer and mixed 5 minutes at 50° C. and 40 rpm. Thetemperature was raised to 150-160° C. and 0.051 g of dicumyl peroxideand 0.471 g of the tetrabutylammonium methacrylate was added. The mixwas reacted for an additional five minutes. The contents of theBrabender™ mixer were removed. A fraction of the reacted polybutadiene(14.76 g) was placed in the Brabender™ mixer along with 33.5 g of BIPMS.The mixture was mixed at 20° C. and 10 rpm for 5 minutes. The Brabender™mixer was then heated to 110° C. at which temperature the speed wasincreased to 80 rpm. Under these conditions, the temperature increasedto 115° C. These conditions were maintained for 5 minutes and then thecompatibilized blend was removed. The compatibilized blend was thencompared to a noncompatibilized blend using electron microscopy. Theresults are reported in Table 1 below.

EXAMPLE 4

Graft Reaction of Nitrile Rubber (Paracril B) with BIPMS Using

Radicals Generated from Peroxide (Dicumyl Peroxide) andTetrabutylammonium 6,8-dithiooctanoate as Radical Trap in a Two Pass Mix

a. The salt was prepared by neutralizing commercially availablematerials: 2064 g of 6,8-dithiooctanoic acid was neutralized with 10.1ml of a 1 molar solution of tetrabutylammonium hydroxide in methanol.The methanol and water were removed under nitrogen to yield a yellowproduct.

b. Two pass compatibilized blend: 47.5 g of nitrile rubber was placed ina Brabender™ mixer and mixed 5 minutes at 50° C. and 40 rpm. Thetemperature was raised to 150-160° C. and 0.051 g of dicumyl peroxideand 0.487 g of the tetrabutylammonium methacrylate was added. The mixwas reacted for an additional five minutes. The contents of theBrabender™ mixer were removed. A fraction of the reacted nitrile rubber(14.76 g) was placed in the Brabender™ mixer along with 33.5 g of BIPMS.The mixture was mixed at 20° C. and 10 rpm for 5 minutes. The Brabender™mixer was then heated to 155° C. at which temperature the speed wasincreased to 80 rpm. Under these conditions, the temperature increasedto 180° C. These conditions were maintained for 5 minutes and then thecompatibilized blend was removed. The compatibilized blend was thencompared to a noncompatibilized blend using electron microscopy. Theresults are reported in Table 1 below.

EXAMPLE 5

Graft Reaction of Polybutadiene with BIPMS Using

Radicals Generated from Peroxide (Dicumyl Peroxide) andTetrabutylammonium Mercaptoacetate as Radical Trap in a Two Pass Mix

a. The salt was prepared by neutralizing commercially availablematerials. 0.9212 g of mercaptoacetic acid was neutralized with 10.1 mlof a 1 molar solution of tetrabutylammonium hydroxide in methanol. Themethanol and water were removed under nitrogen to yield a white product.

b. Two pass compatibilized blend: 47.12 g of polybutadiene was placed ina Brabender™ mixer and mixed 5 minutes at 50° C. and 40 rpm. Thetemperature was raised to 150-160° C. and 0.051 g of dicumyl peroxideand 0.471 g of the tetrabutylammonium methacrylate was added. The mixwas reacted for an additional five minutes. The contents of theBrabender™ mixer were removed. A fraction of the reacted polybutadiene(14.76 g) was placed in the Brabender™ mixer along with 33.5 g of BIPMS.The mixture was mixed at 20° C. and 10 rpm for 5 minutes. The Brabender™mixer was then heated to 110° C. at which temperature the speed wasincreased to 80 rpm. Under these conditions, the temperature increasedto 115° C. These conditions were maintained for 5 minutes and then thecompatibilized blend was removed. The compatibilized blend was thencompared to a noncompatibilized blend using electron microscopy. Theresults are reported in Table 1 below.

EXAMPLE 6

Graft Reaction of Natural Rubber with BIPMS Using

Radicals Generated from Peroxide (Dicumyl Peroxide) andTetrabutylammonium Dithiopropionate as Radical Trap in a Single PassMix.

a. The salt was prepared by neutralizing commercially availablematerials. 2.108 g of dithiopropionic acid was neutralized with 10 ml ofa 1 molar solution of tetrabutylammonium hydroxide in methanol. Themethanol and water were removed under nitrogen to yield a white salt.

b. One pass compatibilized blend: 33.22 g BIPMS and 14.21 g of naturalrubber were placed in a Brabender™ mixer. The rubber was mixed 5 minutesat 100° C. and 60 rpm. The temperature was raised to 150° C. and 0.05 gof dicumyl peroxide and 0.5 g of the tetrabutylammonium dithopropionatewas added. The mix was reacted for an additional five minutes. Thecompatibilized blend was then compared to a noncompatibilized blendusing electron microscopy. The results are reported in Table 1 below.

EXAMPLE 7

Graft Reaction of Styrene-Butadiene Rubber with BIPMS Using Radicals

Generated from Azo-decomposition of Tetrabutylammonium4,4azobiscyanovalerate in a Single Pass Mix

a. The salt was prepared by neutralizing commercially availablematerials. 4.17 g of 4,4azobiscyanovalerate was neutralized with 40 mlof a 1 molar solution of tetrabutylammonium hydroxide in methanol. Themethanol and water were removed under nitrogen to yield a white product.

b. Single pass compatibilized blend: 82.02 g of styrene-butadiene rubber(SBR 1502) and 191.38 g of BIPMS were placed in a B-Banbury™ mixer alongwith 1.37 g of tetrabutylammonium 4,4azobiscyanovalerate. The mix wasdropped at 180° F. after 3 minutes of mixing. The rubber mix internaltemperature was measured with a pyrometer after dropping. The rubber wastypically 50° F. higher in temperature than the Banbury™ droptemperature. The compatibilized blend was then compared to anoncompatibilized blend using electron microscopy. The results arereported in Table 1 below.

All blends were characterized using low voltage scanning electronmicroscopy on osmium stained images. The phase size information wasobtained by sampling the image using lines drawn at random on theimages. The data was collected at two magnifications (9,000 and 20,000).The average dispersed phase for the compatibilized blend and acomparative control are presented in Table 1 below. The smaller thedispersed phase size the more compatibilized the blend.

TABLE 1 Dispersed Phase Size Results for Examples 1-7. CompatibilizedComparative Blend Dispersed Phase Dispersed Phase Example # Size(micrometers) Size (micrometers) 1 0.1 .5 2 0.1 1 3 0.2 2 4 0.7 30 5 0.72 6 0.2 2 7 0.7 3

In addition to controlling the phase size one can practice the reactionin a manner which produces polymer phase inversion. The followingexamples are illustrative of this benefit.

EXAMPLE 8

Graft Reaction of Natural Rubber with BIPMS Using Radicals

Generated from Peroxide (Dicumyl Peroxide) and TetrabutylammoniumThiosalicylate as Radical Trap in a Single Pass Mix.

a. The salt was prepared by neutralizing commercially availablematerials. 1.546 g of thiosalicylic acid was neutralized with 10 ml of a1 molar solution of tetrabutylammonium hydroxide in methanol. Themethanol and water were removed under nitrogen to yield a white salt.

b. One pass compatibilized blend: 33.27 g of BIPMS and 14.24 g ofnatural rubber were placed in a Brabender™ mixer. The rubber was mixed 5minutes at 100° C. and 60 rpm. The temperature was raised to 150° C. and0.05 g of dicumyl peroxide and 0.5 g of the tetrabutylammoniumthiosalicylate was added. The mix was reacted for an additional fiveminutes. The resultant blend comprised a continuous natural rubber phasewith 1 micrometer dispersed phase.

EXAMPLE 9

Graft Reaction of Natural Rubber with BIPMS Using Radicals

Generated from Peroxide (Dicumyl Peroxide) and TetrabutylammoniumThiosalicylate as Radical Trap in a Two Pass Mix

a. The salt was prepared by neutralizing commercially availablematerials. 1.546 g of thosalicylic acid was neutralized with 10 ml of a1 molar solution of tetrabutylammonium hydroxide in methanol. Themethanol and water were removed under nitrogen to yield a white salt.

b. Two pass compatibilized blend: 47.48 g of natural rubber was placedin a Brabender™ mixer and mixed 5 minutes at 50° C. and 40 rpm. Thetemperature was raised to 150-160° C. and 0.051 g of dicumyl peroxideand 0.49 g of the tetrabutylammonium thiosalicylate was added. The mixwas reacted for an additional five minutes. The contents of theBrabender™ mixer were removed. A fraction of the reacted natural rubber(14.35 g) was placed in a Brabender™ mixer along with 33.59 g of BIPMS.The mixture was mixed at 20° C. and 10 rpm for 5 minutes. The Brabender™mixer was then heated to 110° C. at which temperature the speed wasincreased to 80 rpm. Under these conditions, the temperature increasedto 115° C. These conditions were maintained for 5 minutes and then thecompatibilized blend was removed. The resultant blend comprised acontinuous BIPMS phase with a 0.5 micrometer dispersed natural rubberphase.

I claim:
 1. A process for forming a blend comprising mixing a generalpurpose rubber selected from the group consisting of natural rubber,polyisoprene, polybutadiene, nitrile rubber, poly(styrene-co-butadiene)and poly(acrylonitrile-co-butadiene); a halogenatedpoly(isobutylene-co-4-methylstyrene); and a multifunctional agentselected from the group consisting of tetrabutylammonium6,8-dithiooctanoate, tetrabutylammonium dithiopropionate, andtetrabutylammonium mercaptoacetate.
 2. The process of claim 1, whereinthe general purpose rubber is mixed with the multifunctional agentbefore mixing with the halogenated poly(isobutylene-co-4-methylstyrene)polymer.
 3. The process of claim 1, wherein the steps are canied out inthe absence of a solvent.
 4. The process of claim 1, wherein the mixingis performed in one step.
 5. The process of claim 1 wherein thehalogenated poly(isobutylene-co-4-methylstyrene) is brominatedpoly(isobutylene-co-4-methylstyrene).